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Package Management in python

  • PIP
  • Virtualenv
  • virtualenvwrapper

Table of contents

  1. PIP
    1. Packages - file,download and install
    2. Manage
  2. Virtual Env
    1. Project specific dependencies context
  3. Virtualenvwrapper
    1. Making venv more convinient(#modular_func)

1. PIP

Thirdparty dependency library package manager. Always Install pip on venv and not pollute different projects
https://pypi.org - list of all available libraries

  • Find , Download , Install
  • Manage

Check if pip is installed:

pip -V
pip list
pip uninstall
pip show

Better way to call pip if a machine has both python2 and python3

python3 -m pip list
python -m pip list
python3 -m install
python -m install

Where does the package get installed

sys.path = '','/usr/lib/python3.7','usr/local/lib/python2.7/dist-packages'

pip show

Shows the location as :
Location: /Library/Python/2.7/site-packages

2 virtualenv

Isolated context for installing packages. Always work inside venvs.
Contain packages,tools,python etc
Keep them separate from Project source code.

Install the virtualenv at a system level :

sudo python -m pip install virtualenv

Create a base venv folder in the system under which all venvs can br created.

mkdir -p ~/venvs

Inside the venvs folder use the virtualenv command to create as many.
It will create dedicated python interpretor / pip and libraries

virtualenv -p python3 basepython3

Go inside the bin folder and run the activate which activates this venv.
On linux/Mac OS

. ~/venvs//bin/activate

Now when we run python or pip , it will refer to the version in this venv

python -V OR pip -V
python -m pip list
. ~/venvs//bin/deactivate

To create a dump of an env with current state of dependencies. Create a new file requirements.txt.

python -m pip freeze > requirements.txt

To import the dependencies used in another environment to current use the requirements.txt as

python -m pip install -r requirements.txt

SPECIFYING VERSIONS in requirements.txt

  module == 1.2.1
  module >= 1.2.1
  module != 1.2.1

2.1 Projects and VirtualEnvs

What happens when we work on an external project like flask ?

  • Requirements.txt is for your own development and sharing between co-developers.we have control over runtime env.

  • git clone <https://github.com/pallets/flask

  • Special file --> setup.py
    this file has a section : install_requires[]

  • If doing local development of such a project , and dont need the external flask but from my code base :

    python -m pip install -e flask

  • tox.in (auto setup varying environments and run unit tests on all )

3. VENVWRAPPER

  • User firndly wrapper of virtualenv
  • Bind projects with virtualenv